The atoms were actually made after the Big Bang! One of the reasons we think the Big Bang happened is because the amount of helium and hydrogen is what we’d predict from the temperature when the universe was very young.
That’s a great question ridgedasher! And actually it’s one that has physicists scratching our heads too
The main problem is that time is something that is intricately tied to our universe. We’re not even really sure what time *is*. But it is one of the dimensions we live in – the other three are the usual space ones of back/forwards; right/left, up/down.
So the universe is made up of something called spacetime. But now you see the problem – since time is part of our universe, how can you ask a question about what happened before time? Because the concept of “before” is derived from time, which is part of the universe!
So it’s a question that we can never really answer, since our definition of time started at the big bang, so the word “before” has no meaning.
But maybe with more research and discoveries we’ll be able to learn about other universes, or other possibilities, that’ll give us some insight into how to answer this one.